1. Field of the Invention
The present invention is directed to cementitious compositions and relates particularly to a cementitious floor underlayment that includes an alpha calcium sulfate hemihydrate, Portland cement, fly ash, and a beta calcium sulfate hemihydrate.
2. Description of the Prior Art
The scope and content of the prior art related to the present floor underlayment is very broad. It includes the prior art directed to forms of gypsum, plaster, cement and concrete as these are used in construction, insulation, fireproofing, roadwork, pottery, molding, flooring, roofing, wall installation, sealing; as well as methods and apparatuses related to these. We are aware of the following prior art in these areas:
______________________________________ 499,170 2,337,523 2,682,515 3,874,887 3,808,299 581,466 2,347,233 2,690,975 3,179,528 3,852,081 933,036 2,494,295 2,705,223 3,232,778 3,869,018 1,558,783 3,025,176 2,753,608 3,427,374 3,895,018 1,705,088 3,093,505 2,791,511 3,450,548 3,957,522 1,901,056 3,917,489 2,798,003 3,547,840 4,030,939 1,923,370 2,512,996 2,859,530 3,582,376 4,045,237 2,078,289 2,533,263 2,882,175 3,623,898 4,067,939 2,172,076 2,602,785 2,914,413 3,645,750 4,038,044 2,310,023 2,681,863 3,873,332 3,770,859 4,353,748 4,304,704 ______________________________________
The prior art also includes "DURACAL which can do what no cement has ever done," brochure of U.S. Gypsum, 1981; "GYP-CRETE Poured Gypsum Floor Underlayment," brochure of Gyp-Crete Corporation, 1981; and the disclosure of our previous applications: Ser. No. 489,015, filed Apr. 27, 1983; and Ser. No. 655,335, filed Sept. 27, 1984.
Of the prior art we have listed, we consider the following as pertinent to our invention: U.S. application Ser. No. 489,015; U.S. application Ser. No. 655,355; U.S. Pat. Nos 4,067,939; 4,075,374; 3,645,750; 3,582,376; 4,353,748; 2,791,511; "A Ready Mix Concrete Company's Experience With Fly Ash," by James E. Cook; E.P.A. "Guidelines For Federal Procurement Of Cement and Concrete Containing Fly Ash," Federal Register, Vol. 48, No. 20, Jan. 28, 1983. None of them taken alone or in any possible combination teaches or suggests our new composition of matter.
For five years we have worked to perfect the unique quick-setting composition which we claim here as our invention. The level of skill of a person of ordinary skill in the art pertinent to this invention is that of a person with familiarity with plasters, gypsums, and cements and various additives for them who has had extensive actual experience formulating them in various combinations to solve problems related to quick-setting compositions of matter.